Many aqueous liquid compositions that form coatings on metal surfaces that protect the metal surface while it is being cold worked are known. The previously most effective ones have generally been zinc, calcium, and/or sodium soaps applied over a preceding heavy phosphate conversion coating on steel substrates or over a complex calcium aluminate conversion coating on aluminum substrates. (Normally, a sodium stearate or other sodium soap salt is applied over a zinc phosphate coating or a calcium aluminate coating. Reaction between the sodium soap and the zinc or calcium in the previous conversion coating is believed to result in both zinc or calcium soap and sodium soap layers, and this type of lubricant is accordingly often called a “reactive” lubricant.) However, this combination is environmentally disadvantageous, especially when used over phosphate coatings, because the liquid compositions used to form phosphate coatings generally contain some types of metal ions, such as those of zinc, nickel, manganese, and/or the like, that are regarded as polluting. Zinc and calcium soaps are substantially insoluble in water, but cause workplace nuisances at best and hazards at worst because they tend to form fine dust particles in the air around sites of cold working processes when used as cold working lubricants. This combination is also economically disadvantageous because it normally requires separate conversion coating and lubricant coating process steps, with associated requirements for equipment for large scale practice of cold working using this method of lubricating the metal substrates being worked.
Various polymer based lubricants have been taught in the art as replacements for the combination of stearates over zinc phosphate conversion coatings, but heretofore none of the polymer based lubricants have proved to be commercially acceptable in all applications. A frequently objectionable feature of commercial use of prior polymeric lubricants is the presence of scratches on the surface of the cold worked article.
Previous attempts to combine the best features of conversion coatings and other lubricants in a single step resulted in the issuance of U.S. Pat. Nos. 4,289,546 and 4,289,547, which have many disclosures in common, and in earlier patents cited in these two patents. In long term practice, the teachings of all of these patents proved to be commercially unacceptable for use on steel, which is the most common substrate treated for protection during cold working, because iron cations dissolved from the steel eventually accumulated in the working compositions to such an extent as to make their continued use unsatisfactory.
More recently, U.S. Published Patent Application No. 2004-0226629A1 disclosed a composition for forming a combined conversion and lubricating coating on a metal substrate comprising an oxyethylated aliphatic alcohol whose aliphatic hydrocarbon moiety contains 18 or more carbon atoms and dissolved phosphate anions. The conversion and lubricating coating is generated in a heated phosphating bath. One drawback of this composition and process was sludging in the bath, due to dissolution of iron during formation of the conversion coating. The iron in the bath generated iron phosphate particles. During use, the concentration of particles eventually reached a concentration where the particles were incorporated into the lubricating coating, which resulted in galling and scratching of workpieces.
Applicants herein have overcome the drawbacks of these prior art conversion coating/lubricant baths by delaying most of the passivating reaction of the metal substrate with the coating composition until after the substrate has been removed from the coating bath.
A major object of this invention is to provide lubricants and processes that will eliminate or at least reduce the environmental and other disutilities noted above while still achieving cold working performance that is adequate when compared with the prior art use of phosphate conversion coatings followed by zinc soap application and to other single step lubricants commonly used in cold forming. Other alternative or concurrent objects are to reduce total energy and/or other costs of cold forming operations, particularly by reducing process related waste of objects being cold worked, more particularly because of rejection for scratched surfaces, and/or by achieving reduced press tonnages required for forming operations. Still another alternative or concurrent object is to provide a lubricant satisfactory for extruding under the more severe conditions in current commercial practice.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, throughout this description, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ by chemical reactions specified in the description, and does not necessarily preclude other chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole (any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention); and the term “mole” and its grammatical variations may be applied to elemental, ionic, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules.